So-called self-learning functions are designed to detect and to store the properties and/or the tolerance situation as well as the drift over the service life of a component of the injection system during the operation of a common-rail injection system, and to compute corresponding correction values; this is disclosed in publication DE 10 2004 006 694 A1, for example.
Furthermore, devices are known for checking the fuel pressure which do not have a metering unit (MU) and in which a fuel pump (EFP) is used directly as the actuator for the rail pressure control. In these devices, a so-called pump characteristic curve results from the cooperation of various components, e.g., the EFP, the high-pressure pump, the EDC, and the lines as the characteristic curve for the high-pressure control.
Publication DE 10 2006 000 238 A1 discusses a control unit for a fuel supply system which has a common-rail accumulator for fuel which is supplied to an internal combustion engine via an injection. A learning device provided here stores the characteristic curve deviations which are computed by a first and a second computing device in a backup storage as learning values.
A method for controlling an internal combustion engine is discussed in publication DE 10 2007 036 684 A1. In this case, the adaptation of a state of a fuel vapor flushing system of the internal combustion engine and an adaptive learning of a characteristic curve of the fuel supply system are provided. A routine may, for example, include the adaptive learning of injector characteristic curves, fuel pump characteristic curves, or air metering errors.
Publication DE 10 2004 053 124 A1 discusses a common-rail fuel injection system. A control unit, which is also described, includes a learning device which controls a metering valve control value supplied to an intake metering valve of the common-rail fuel injection system in order to control the opening degree of the intake metering valve. The learning device controls the metering valve control value in such a way that the opening degree of the intake metering valve continuously increases starting from a preset value, which is lower than a limiting value, which implements the maximum ejection rate of the high-pressure pump, for implementing a maximum ejection rate. The learning device includes the instantaneous metering valve control value, which is supplied to the intake metering valve, as a maximum ejection rate control value, the learning device learning that the high-pressure pump reaches the maximum ejection rate at the maximum ejection rate control value.